Governments and industrial concerns on a priority basis are dedicating increased attention to alternatives to petroleum as sources for fuels and chemical intermediates, i.e., coal and wood. Substantial reserves of coal exist in highly industrialized countries, and wood is both plentiful and replenishable worldwide.
Since most current energy utilization technology requires liquid energy media, it has become an important research and development objective to provide innovative means to convert coal into liquid sources of potential energy.
It was recognized by early workers that coal can be liquified by controlled heating in the substantial absence of oxygen. The conversion products are a liquid and a char. Because of the new compelling economic factors, the technology of coal liquefaction and gasification has been expanding at an accelerated pace. Pioneer developments in the field are represented by Lurgi and Fischer-Tropsch technology.
A broad variety of organic solvents have been proposed for solubilizing coal. Most of the solvent media have disadvantages of high cost, poor solvation capacity for coal constituents, high viscosity, and the like. Coal tar, recycle coal oil, petroleum refinery byproduct streams, and propane-deasphalted petroleum tar, are among the coal solvation solvents disclosed in the prior art. Recent advances in coal liquefaction are described in U.S. Pat. Nos. 1,904,586; 1,955,041; 1,996,009; 2,091,354; 2,174,184; 2,714,086; 3,375,188; 3,379,638; 3,607,718; 3,640,816; 3,642,608; 3,705,092; 3,849,287; 3,870,621; inter alia.
There remains a pressing need for new technology for the conversion of coal into liquid carbonaceous products to complement and to enhance conventional petroleum-derived commodities. Innovative processes for liquefaction of coal are required which are not dependent on high pressures or reducing gases or catalysts for efficient and economic liquefaction of coal.
Accordingly, it is an object of the present invention to provide an improved method for converting solid carbonaceous materials into liquid derivatives.
It is another object of the present invention to provide a process for liquefaction of carbonaceous materials without the need for high pressures or reducing gases or catalysts.
It is another object of the present invention to solubilize coal to form homogeneous solutions which are directly applicable as liquid fuels, pitch compositions, asphaltic cements, and the like.
It is a further object of the present invention to upgrade low value refractory petroleum residua from refinery operations into liquid fuel and other high value commercial products. Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.